Lesson Learned
by checkmate14
Summary: In which Bruce is being excessively flirty in class and manages to persuade his teacher/boyfriend that sex would be a good idea right about now.


**_Also posted on my AO3 page under the username 'checkmate'. Enjoy!_**

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"Excuse me? _Sir_?"

Tony looked up from the truly abysmal essay he was being forced to read to see Bruce Banner's hand waving in the air, trying to catch his attention. "Banner, please don't call me 'sir', it makes me feel old. It's Tony."

Bruce smirked. "Please don't call me 'Banner', it makes me feel young. It's Bruce."

Tony had to tear his eyes away and focus back on Bruce's face as he slowly twirled his pen around his fingers, all while sending Tony that same cocky grin. "Tony, then." The name rolled off his tongue seductively, and heat crawled up Tony's neck at the blatant flirting in his student's tone. "I have a bit of a problem, and I thought you could maybe help me out? I'm finding it a little _hard_."

Tony pinched the bridge of his nose tightly, and took a deep breath as subtly as he could. Hoping desperately that the fact that he was starting to get hard wasn't visible through his trousers, he stood and walked over to Bruce's desk, and looked at his notebook over his shoulder. Every answer was filled in and correct.

"Ah." Tony said, trying to keep a straight face, not sure whether he really wanted to laugh or groan (or both). "I see what you've done." He pulled a second stool up to the desk and sat down, his knee knocking against Bruce's. "What the _hell_ are you playing at?" Tony hissed.

"I don't know, _sir, _I think I just forgot how to answer this question." Bruce said loudly, and Tony kicked him under the table. Tony groaned under his breath as he pulled out a pen and pretended to show Bruce how to calculate rates of radioactive decay. "You know, I wasn't joking. About the hard thing." Bruce muttered quietly, so that only Tony could hear. "I've just been sat here for the whole lesson, thinking about you."

"That made you hard, did it? God, I wish I had the energy of a teenager still."

"Fuck off, Tony, you are hard as a fucking rock right now. I can tell." Bruce dismissed. Tony kicked him again, but didn't deny it. "And no, that wasn't what made me hard. What made me hard was thinking of how bored you looked marking those papers, and then thinking about what you'd look like if I was sucking you off at the same time."

Tony's pen clattered to the floor, and the kids on the next desk gave him a strange look. One of the girls, seeing that Tony had made no signs of planning to fetch it, picked it up as passed it to him awkwardly. He nodded. "Thank you, Natasha." He said, his voice sounding a little strained. "Bruce, you are the worst kind of person, you know that?" He growled, when she was safely back in her seat.

"Perfectly aware, thank you very much." Bruce grinned.

"Mr. Stark? Er, Tony?" A strawberry blonde in the second row asked cautiously. "We've done the questions, what do you want us to do now?"

Tony looked in horror from Bruce to Pepper, and then subtly down into his lap, where his cock had made a clearly visible bulge in the fabric. "Um…" He swallowed, but his throat was dry. "Just give me two more minutes with B- two more minutes for everyone else to finish, and then we'll move on, okay?"

Pepper nodded, and Tony turned back the Bruce in horror. "Don't you _dare_ try anything." He threatened, screwing up his eyes and trying to think of anything but getting a blow job from his student.

"So you don't want a hand then?" Bruce asked, his voice light and teasing. Tony kicked him for a third time, even harder than the previous two.

"Shut. Up." He whispered. _Cold showers, dead puppies, erm… Making out with Steve Rogers in the World History department? _He thought desperately. Something seemed to work, by any means. After another minute, he was able to stand up without embarrassing himself in front of twenty eighteen year olds.

He set them an experiment to be getting on with, as he returned to his mountain of essays, and began reading through them wearily, trying hard to keep his mind off the fact that just a few meters away, he could be sure that Bruce Banner was picturing sucking him off. He gulped.

"_Tony_?" That same smooth voice interrupted his thoughts once again.

He sighed. "Yes, Bruce?"

"Clint's not here today- he has a hangover- so I don't have a lab partner."

Tony stared him down. "Well then, Bruce, since it's not safe for you to do this practical by yourself, I suppose you have two options. You could, one, join another pair and work as a three-"

"I don't like working with other people." He interrupted instantly, eyeing Tony meaningfully.

"-Or two, you can sit there and copy out of the textbook backwards until the end of the lesson." He said firmly, and promptly returned to his marking, the grin spreading across his face hidden by the angle he held his head.

"But I thought, maybe-"

"_No."_

Bruce huffed and marched over to where Natasha and Pepper were setting up, sending reproachful looks towards Tony every few minutes, which he steadfastly ignored. Three truly awful papers later, there was a loud _SMASH! _and Tony was not at all surprised to see Bruce with a pile of shattered glass, which used to be a test tube, at his feet. "Oops." He said, smirking a little, his eyes meeting Tony's.

"Bruce, stay behind after class, please." Tony instructed firmly. "And sweep all of that up immediately, before it gets everywhere." Bruce's face lit up, and with a gleam in his eye, he swept up the broken glass, and tipped it into the bin.

The bell signalling the end of the lesson rang soon after, and once the final student had shut the door behind them, Bruce flew at Tony and forcefully pushed their lips together, his hands clawing desperately in Tony's messy dark hair.

The older man pushed him back easily. "Bruce, cut it the fuck out." He said, anger taking over his tone. "Care to explain what the _hell_ that was all about?" He could barely keep his voice at a volume that wouldn't be heard out in the corridor.

Bruce bit his lip. "What_what_ was about?" He said, confused.

"The innuendo, the dirty talk, the calling out for attention… For fuck's sake, Bruce, I really like you, I do, and I wouldn't be doing this if I didn't, but we have to keep it a secret, at least until you graduate. This is my job, and your future, and we're not throwing that away because you're a horny smart ass. If you do anything like that in class again, I'm calling this off. I thought you were more responsible than that."

Bruce closed his eyes and hung his head, ashamed. "Shit, I'm sorry, I didn't think, I just… You're just so… I'm really sorry." He ended pathetically. Tony wrapped his arms around him gently.

"It's fine, Bruce, just… Just never do that again, yeah? We can't risk it, and I don't want to lose you." Tony put two fingers gently under Bruce's chin and lifted it so that their eyes met, then carefully pressed his lips against Bruce's. The kiss was sweet and gentle, and Tony felt Bruce smiled softly against his mouth. "It would totally ruin the moment if I told you I really want to fuck you over my desk right now, wouldn't it?" Tony asked, pulled away a little.

Bruce was silent for a second, and then started laughing. "Probably." Bruce agreed. "But I seriously do not care."

"Alas, you and I may not, but I'm pretty sure that Fury will if he walks in on us. Subtly and shit, remember?" Tony said regretfully.

"The supply closet?"

Tony laughed. "Incorrigible, the youth of today. Incor-fucking-rigible." Bruce grabbed Tony by the upper arm and pulled him into the tiny space, most of which was taken up by a series of shelves and a single chair, slamming the door behind him. Tony flicked on the light. "Condom? Lube? They're in my bag? Outside?" He said, raising an eyebrow.

Bruce laughed, and pulled out his wallet. "I'm a teenager, Tony. Always horny, always prepared." And with that, he tossed a condom and a sachet at his teacher. "Hmm… This closet seems bigger when you're not trying to have sex in it."

Tony swiftly stripped off his clothes and threw them into a corner. "We'll manage." He tore open the lube with his teeth and coated his fingers with it liberally, then smirked at the still fully clothed Bruce. "You are not nearly naked enough." He said, narrowing his eyes, and Bruce blushed a little and tugged off his jeans awkwardly.

When they were both in a sufficient state of clotheslessness, Tony pulled Bruce closer and captured the boy's mouth firmly with his own, before reaching down to tease Bruce with his slicked up fingers, but he was surprised to find his lover already a little stretched. Tony pulled away as much as he could in the space and smirked, as Bruce bit his lip and blushed. "I, um. I was hoping-"

"Jesus, I could guess that, you fucker." Tony moaned, slipping a single finger into Bruce easily. The boy tensed a little, but soon relaxed, a small whimper escaping from his lips. Tony quickly added a second, and twisted them, causing Bruce to groan loudly and begin grinding against Tony's thigh. "Slow down, kid." Tony laughed. "Think you can hold out at least until I actually get my dick in you?"

"Can you make it quick?" Bruce gasped, panting as Tony added a third finger and started a ruthless rhythm of pumps into his ass.

"Your wish is my command." Tony said smoothly, and pulled his fingers out suddenly, leaving Bruce whining at the loss.

"How the fuck are we going to do this?" He said, looking around the cramped space mainly (and regretfully) full of small bottles of dangerous chemicals that neither of them really wanted smashed during sex.

Tony inclined his head towards the single chair situated in the corner, and pulled it into the middle of the space before sitting down on it. Bruce gave him an odd look, and Tony ignored it, rolling the condom on to his steadily leaking dick, trying as hard as he could to bite back the moans threatening to spill from his lips. "Come over here." He said quietly, and Bruce was stood facing him, looking confused. Tony placed his hands on Bruce's hips and guided him down until the boy was straddling his lap.

Bruce's eyes lit up with understanding. "Seriously?" He said sceptically. "I don't… I've never…"

Tony shushed him. "It's fine. You'll love it." He smeared the last bit of lube over the condom awkwardly, then his eyes met Bruce's. "Ready?"

Bruce's breath hitched nervously, and he nodded. "Ready."

Tony lifted his hips gently, until Bruce took his own weight, and Tony lined up his cock. Bruce took a deep breath, and lowered himself down slowly. "Oh, _fuck." _He whispered, throwing his head back. "Fuck, fuck, fuck, fuck, _fuck_!" His voice had shot up in pitch and hands were clenched on the back of the chair. Tony carefully removed them and squeezed them encouragingly.

"How do you feel?" Tony murmured in his ear. Bruce lowered himself a little more at a time, until he was sat on Tony's lap again, with his lover's (and teacher's) dick filling him and his eyes streaming. "Are you okay?" He asked, his voice edged with worry when Bruce didn't answer.

"I'm fine, sir." He said breathlessly, after taking another minute to collect himself. "I'm more than fine. I'm _incredible_."

Tony chuckled lightly. "You sure are that. Do you want to, you know, move or something? I'm kind of dying here."

Bruce blushed. "Oops." He said, experimentally lifting his weight a little bit, then dropping back down. Both he and Tony gasped. The burn and the friction felt amazing, and sent shudders of pleasure through the older man. His hips thrust up involuntarily, desperately seeking more, and Bruce ground down at the exact same moment. Tony's dick pressed against Bruce's prostate, and the student let out a scream. Tony quickly covered his mouth with one of his hands, and Bruce gulped.

"Try and stay a little bit quiet, Banner? Again, subtly and shit." Tony raised an eyebrow, and Bruce nodded. Tony pressed another kiss to Bruce's mouth, and then down his neck and across his shoulders, while Bruce started up a rhythm, which was irregular enough that Tony couldn't quite predict when the next thrust was going to come. He tried to match it, but couldn't quite keep up every time, especially as the thrusts became more and more erratic.

"I'm sorry, sir, I can't- I'm not…" Tony understood, and wrapped a hand around Bruce's dick firmly, and because stroking at the same pace as his hips thrusting upwards. It wasn't long until Bruce's come splattered against Tony's chest, and the boy slumped back in exhaustion. "_Fuck."_

Bruce's muscles had seized up as he came, and the tightness and pressure around his dick had brought him so close to the edge. "Bruce, you might wanna…" He warned, as his hips thrust up against Bruce's oversensitive prostate, still seeking the last bit of friction to allow him to drop over the edge. Bruce whimpered, too spent to make more of a protest than that, as pleasure edged with pain surged through his body, before Tony climaxed, crying out Bruce's name as he released inside him.

Bruce stood shakily as Tony's cock went soft inside him, and surveyed the scene in front of him. Tony, his chest splattered with white, was leaning back into the chair, breathing deeply. Bruce leant down and peeled off the spent condom, tying it off and discarding it temporarily to the floor as he set about cleaning the sticky substance from his dick with his tongue. "Bruce, you are the fucking best, you know that?" Tony murmured weakly.

"I'd clean off your chest too, but I think we'd both get hard again, and while I have no objection to further sex, it's probably not the best time." Bruce laughed.

Tony laughed weakly in return. "Probably not." He agreed. "Although I wouldn't object to the help you offered earlier, regarding those damn Chemistry essays?"

"I will be at your place at seven." Bruce said, a smile spreading across his face. "But for now, we should probably get dressed and pretend we didn't just have hot illegal sex in your storage cupboard."

"You probably should have worn a condom too." Tony said, looking down at his chest regretfully. "It would have made this bit so much easier."

Bruce shrugged. "We'll remember next time. Learn from your mistakes and all that."

"Next time?" Tony said, his eyebrows raised as he pulled his underwear and pants back on, then pulled a crumpled up tissue from his pocket and attempted to wipe off the worst of the stickiness across his body.

"Like fuck we're never doing that again." Bruce said flatly. "Come off it, _sir._" He said pointedly.

"Oh, and that's another thing." Tony said, smirking. "Did you really get off on calling me 'sir' mid-sex?" Bruce flushed red. "Shit, Bruce, you are so fucking kinky." Tony groaned. "Get out of my sight, before I need another fuck."

Bruce did up the final button on his shirt, and snatched up a tray of chemicals as a cover for why they'd been in the closet in the first place, when Tony stopped him. "Leave the top one undone." He instructed, unbuttoning it for him. "It's hot. Now get out of here, quickly."

Bruce smirked and pushed the door open. "Fuck off, Tony. I'll see you later."

"You bet you will." Tony laughed, following him out of the closet.

And then they froze.

"Oh, um. I just came to leave this on your desk? It's from Mr Rogers, in World History?" A nervous freshman squeaked, thrusting the envelope at Tony nervously and scuttling out of the room.

Tony opened it warily. "Oh, fuck." He breathed.

"What?" Bruce said, panicking.

_"You two seriously need to learn something about morality, or failing that, subtlety, or you're going to ruin both of your lives. – Steve." _Tony read out. "I am going to kill that fucker."

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**AN: All feedback is greatly appreciated!**


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